Thick steel plate cooling device and cooling method, and thick steel plate manufacturing facility and manufacturing method

Abstract

The invention provides a thick steel plate cooling device, a thick steel plate cooling method, thick steel plate manufacturing equipment and a thick steel plate manufacturing method. In the cooling device for a thick steel plate, the ratio P / D of the spacing P of the restricting rollers to the diameter D of the restricting rollers is 2.0-2.5, a plurality of cooling headers are arranged between the restricting rollers, each cooling header is connected with any one of more than two cooling water supply systems, each cooling header is provided with a plurality of cooling nozzles along the width direction of the steel plate, and the cooling nozzles are arranged in the width direction of the steel plate. The cooling nozzles adjacent to each other in the width direction of the steel plate are connected to the cooling headers of different cooling water supply systems, and the flow densities of the cooling water sprayed from the cooling nozzles adjacent to each other in the width direction of the steel plate are set to be different, and the cooling device is provided with a control means for controlling the flow densities of the cooling water sprayed from the cooling nozzles adjacent to each other in the width direction of the steel plate. And a control means for performing control using the adjustment valves so as to individually select the cooling water supply systems and spray the cooling water from the cooling nozzles.

Description

[0001] This application is a divisional application of an invention patent application with an application date of December 14, 2018, application number 201880081519.3, and invention name “Cooling device and cooling method for thick steel plates, and manufacturing equipment and manufacturing method for thick steel plates”. Technical Field

[0002] The present invention relates to a cooling device and a cooling method that can control the shape and adjust the cooling rate within a wider range than before when controlled cooling after hot rolling or cooling the steel plate cooled to room temperature after hot rolling by reheating and quenching in a production line for thick steel plates. Furthermore, the present invention relates to a manufacturing equipment for thick steel plates using the cooling device and a manufacturing method for thick steel plates using the cooling method. Background Art

[0003] In particular, in the manufacture of thick steel plates (sometimes simply referred to as steel plates), it is necessary to ensure the mechanical properties required of the steel plates, especially strength and toughness. In order to achieve this, the high-temperature thick steel plates after rolling are cooled as they are, or temporarily air-cooled to room temperature and then reheated / quenched offline. In this cooling operation, the steel plates are often cooled at a fast cooling rate in view of the material properties required of the steel plates, especially the high strength.

[0004] On the other hand, due to the recent high degree of material control, not only the demand for high strength has increased, but also the demand for combining soft phase transformation structures with hard phase transformation structures has increased. For example, there is a method of obtaining a composite structure such as ferrite + bainite or ferrite + martensite by setting the cooling rate to a relatively slow condition in the early or late stages of cooling. Through this composite organization, there is the possibility of producing, for example, a steel plate with excellent seismic resistance and the ratio of yield strength to tensile strength, i.e., yield ratio, which can be reduced.

[0005] In the past, in order to achieve such a composite organization in thick steel plates, a multi-stage heat treatment was performed by performing reheating and quenching multiple times. However, in order to save the process, a cooling technology that can change the cooling rate at any time during a single quenching is required. In particular, in order to promote the formation of ferrite, it is necessary to cool for a long time at an extremely slow cooling rate (for example, about 2 to 20°C / s). Therefore, compared with the cooling rate of a general online controlled cooling device or a quenching device during heat treatment (about 30 to 60°C / s for a plate thickness of 20 mm), it is required to adjust to an extremely slow cooling rate.

[0006] As a technique for changing the cooling rate at an arbitrary timing in the cooling process of a thick steel plate, there are the following patent documents.

[0007] Patent Document 1 discloses a technique for changing the cooling capacity over a wide range by changing the liquid level of the water tank, which is provided with a water tank and a nozzle disposed in the water tank, with respect to the cooling manifold below. In Patent Document 1, when the cooling capacity is increased, the liquid level of the water tank is increased so that the tip of the nozzle is immersed in water, and the water in the water tank is accompanied by the sprayed water in addition to the sprayed cooling water, so that the steel plate can be exposed to a larger amount of water than the spray flow rate of the nozzle. Furthermore, when the cooling capacity is reduced, the liquid level of the water tank is reduced so that the tip of the nozzle is not immersed in water, and the aforementioned accompanying flow is avoided, so that the steel plate can be exposed to a smaller amount of water. On the other hand, in such a technique, a water tank needs to be arranged between the rollers, so that the cooling is limited to the lower surface of the steel plate, and cannot be used for cooling the upper surface. In addition, in equipment with a narrow roller interval such as a quenching device for thick plates, it is impossible to set the water tank between the rollers.

[0008] Patent Document 2 is about a technology that installs a plurality of nozzles in the width direction, supplies water from adjacent nozzles from independent systems, and adjusts the flow rate by spraying only one of them when the flow rate is reduced. On the other hand, even with such a technology, the adjustment margin of the flow rate can only be adjusted by about 50% relative to the maximum cooling rate.

[0009] Therefore, in order to improve the above-mentioned points, Patent Document 3 records the following technology: a rapid cooling device and a slow cooling device having rod-shaped cooling water nozzles with different flow characteristics are arranged in front and behind, and the rapid cooling device and the slow cooling device are switched in a cooling area to perform spraying, thereby adjusting the cooling speed in a wide range.

[0010] Prior Art Literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 59-47010

[0013] Patent Document 2: Japanese Patent Application Publication No. 2014-124634

[0014] Patent Document 3: Japanese Patent Application Publication No. 2011-167759 Summary of the invention

[0015] Problems to be solved by the invention

[0016] The cooling of thick steel plates, especially in offline heat treatment, is often done by so-called roller quenching, which is a process of cooling the steel plates by restricting them with rollers. This method is widely used because the steel plates are cooled by restricting them with rollers, so the flatness of the cooled steel plates is good, and the subsequent shape correction process can be reduced. On the other hand, roller quenching uses relatively large diameter rollers to make the cooling shape good, and restricts the steel plates with a narrow roller spacing, so it is impossible to ensure a large space for the cooling device set between the rollers. Therefore, it is difficult to apply the technology of Patent Document 3 to the cooling device of the roller quenching type.

[0017] Therefore, the present invention is made in view of the above situation, and its purpose is to control the shape of the thick steel plate and adjust the cooling rate in a wide range by adjusting the cooling water volume in a wide range, and in particular, in a roller quenching type cooling device in which a cooling device is provided between rollers for limiting the thick steel plate, to provide a cooling device and a cooling method that are effective for a narrow cooling space. Furthermore, the present invention aims to provide a manufacturing equipment for thick steel plates using the cooling device and a manufacturing method for thick steel plates using the cooling method.

[0018] Solutions to Solve Problems

[0019] As a result of careful studies, the inventors have discovered that the shape of the steel plate can be controlled by setting the ratio P / D of the limiting roll pitch P to the limiting roll diameter D within a specified range, and that the cooling rate can be adjusted over a wide range by using cooling nozzles with different flow densities.

[0020] The gist of the present invention is as follows.

[0021] [1] A cooling device for thick steel plates, wherein a plurality of limiting rollers are arranged along the conveying direction of the steel plates and a plurality of cooling headers are arranged between the limiting rollers, wherein:

[0022] The ratio P / D of the limiting roller pitch P to the limiting roller diameter D is set to 2.5 or less.

[0023] Each cooling header is connected to any one of two or more cooling water supply systems.

[0024] Each cooling water supply system is equipped with a regulating valve to independently open and close the water supply and control the flow rate.

[0025] Multiple cooling nozzles are installed on each cooling header along the width direction of the steel plate.

[0026] The adjacent cooling nozzles along the width direction of the steel plate are respectively connected to the cooling headers of different cooling water supply systems, and,

[0027] The flow densities of cooling water sprayed from adjacent cooling nozzles in the width direction of the steel plate are set to different flow densities. For the same spraying pressure, the cooling water sprayed from the cooling nozzle spraying the largest flow density can spray cooling water with a flow density three times or more than that from the cooling nozzle spraying the smallest flow density.

[0028] The cooling device for a thick steel plate includes a control mechanism that performs control using a regulating valve so as to individually select each cooling water supply system and spray cooling water from a cooling nozzle.

[0029] [2] The cooling device for thick steel plates according to [1], wherein the distance from the front end of each cooling nozzle to the steel plate is set to a position within a range of ±50 mm or less relative to the height of the center axis of the limiting roller.

[0030] [3] A cooling device for thick steel plates according to [1] or [2], wherein each cooling nozzle is any one or more of a flat nozzle, a full cone nozzle, a square spray nozzle, and an elliptical spray nozzle, and the spray angle of the cooling water when the cooling water is sprayed from each cooling nozzle is in the range of 60 to 120 degrees.

[0031] [4] A method for cooling a thick steel plate, using a cooling device having a plurality of restraining rollers arranged along a conveying direction of the steel plate and a plurality of cooling headers disposed between the restraining rollers, wherein:

[0032] The ratio P / D of the limiting roller pitch P to the limiting roller diameter D is set to 2.5 or less.

[0033] Each cooling header is connected to any one of two or more cooling water supply systems.

[0034] Each cooling water supply system is equipped with a regulating valve to independently open and close the water supply and control the flow rate.

[0035] Multiple cooling nozzles are installed on each cooling header along the width direction of the steel plate.

[0036] The adjacent cooling nozzles along the width direction of the steel plate are respectively connected to the cooling headers of different cooling water supply systems, and,

[0037] The flow densities of cooling water sprayed from adjacent cooling nozzles in the width direction of the steel plate are set to different flow densities. For the same spraying pressure, the cooling water sprayed from the cooling nozzle spraying the largest flow density can spray cooling water with a flow density three times or more than that from the cooling nozzle spraying the smallest flow density.

[0038] Each cooling water supply system is individually selected and controlled by using a regulating valve so that cooling water is sprayed from the cooling nozzle.

[0039] [5] The method for cooling a thick steel plate according to [4], wherein the distance from the front end of each cooling nozzle to the steel plate is set to a position within a range of ±50 mm or less relative to the height of the center axis of the limiting roll.

[0040] [6] A method for cooling a thick steel plate according to [4] or [5], wherein each cooling nozzle is any one or more of a flat nozzle, a full cone nozzle, a square spray nozzle, and an elliptical spray nozzle, and the spray angle of the cooling water when the cooling water is sprayed from each cooling nozzle is in the range of 60 to 120 degrees.

[0041] [7] A thick steel plate manufacturing facility comprising the cooling device described in any one of [1] to [3].

[0042] [8] A method for manufacturing a thick steel plate, comprising a cooling step using the cooling method described in any one of [4] to [6].

[0043] Effects of the Invention

[0044] According to the present invention, during cooling of a thick steel plate, the shape can be controlled and the cooling rate can be adjusted within a wide range, so that thick steel plates with various strengths can be manufactured. In addition, the present invention is particularly effective for a narrow cooling space such as a cooling device provided between limiting rollers provided at narrow intervals along the conveying direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of an off-line heat treatment facility for thick steel plates using the cooling device of the present invention.

[0046] Figure 2 This is a schematic diagram showing one embodiment of the cooling device of the present invention.

[0047] Figure 3 It is a diagram for explaining the positional relationship between the cooling nozzle and the regulating roller according to the present invention.

[0048] Figure 4 It is a diagram showing the spray angle of cooling water (spray water) sprayed from the cooling nozzle.

[0049] Figure 5 is a schematic diagram of the cooling device of the present invention viewed from above, Figure 5 (a) is a diagram showing the structure of a cooling header. Figure 5 (b) and (c) are diagrams showing the state of spray water ejected from the cooling nozzle.

[0050] Figure 6 This is a diagram showing the arrangement of cooling headers and cooling nozzles when the cooling header system is multiplied (four systems).

[0051] Figure 7This is a picture showing the collision of the spray water from the small-flow cooling nozzles and the thick steel plate when cooling water is sprayed from the dual-system cooling headers. Figure 7 (a) is the case where a flat nozzle is used. Figure 7 (b) is the case where an elliptical nozzle is used. Figure 7 (c) is the case where a full cone nozzle is used. Figure 7 (d) is the case where a square blowing nozzle is used.

[0052] Figure 8 This is a schematic diagram of the situation where the nozzle spacing is different for a large flow cooling nozzle and a small flow cooling nozzle. Figure 8 (a) is a diagram showing the structure of a cooling header. Figure 8 (b) is a diagram showing the spray water of a large flow cooling nozzle. Figure 8 (c) is a diagram showing the state of spray water from a small flow rate cooling nozzle.

[0053] Fig. 9 This is a schematic diagram of a cooling treatment facility for a thick steel plate using the cooling device of the present invention.

[0054] Fig.10 This is a graph showing the relationship between the injection pressure and the flow rate density in the large flow rate cooling nozzle and the small flow rate cooling nozzle.

[0055] Fig.11 This is a graph showing the relationship between the cooling rate and the flow rate density from 800° C. to 400° C. at the center in the plate thickness direction when the steel plate is cooled. DETAILED DESCRIPTION

[0056] Embodiments of the present invention will be described with reference to the drawings.

[0057] Figure 1 This is a diagram illustrating the application of the cooling device of the present invention to the offline heat treatment of thick steel plates. The thick steel plate S is processed into a predetermined thickness (e.g., 40 mm) and width (e.g., 2500 mm) by a rolling machine in advance, and is transferred to a formal heat treatment production line, and then heated to a predetermined temperature (e.g., 920°C) by a heating furnace 1, and then cooled by a cooling device 2 provided on the output side of the heating furnace 1. The cooling device 2 is composed of a roller table roll 3 for transferring the thick steel plate S, a limiting roll 4 for limiting the thick steel plate S, and a cooling header 5 provided on the upper and lower surfaces of the thick steel plate S.

[0058] Figure 2 Detailed description of the cooling device 2 according to one embodiment of the present invention is shown. Figure 2As shown, there are multiple rollers 3 for conveying thick steel plates S and multiple limiting rollers 4 for limiting thick steel plates S, and multiple large-flow cooling manifolds 51 and multiple small-flow cooling manifolds 52 are provided on the upper surface and the lower surface between the limiting rollers 4 (between the rollers 3). In each cooling manifold, a flow meter 6 is used to measure the flow rate of cooling water supplied to the cooling manifold, and a flow regulating valve 7 is provided so that it can be adjusted to a specified flow rate based on the measured result. Moreover, the flow regulating valve 7 is connected to a control mechanism (not shown) and can individually set the opening and closing (water supply / cut-off) of the cooling water. It should be noted that multiple cooling nozzles 53 (54) are installed on each cooling manifold. The cooling nozzles 53 (54) will be described in detail later.

[0059] The following describes the positional relationship between the cooling header (cooling nozzle) on the upper surface of the thick steel plate and the limiting roller 4. It should be noted that the spacing between the roller table rollers 3 and the limiting rollers 4 is the same. Therefore, the positional relationship between the cooling header (cooling nozzle) on the lower surface of the thick steel plate and the roller table roller 3 is the same as the positional relationship between the cooling header (cooling nozzle) on the upper surface of the thick steel plate and the limiting roller 4.

[0060] Figure 3 : This is a diagram illustrating the positional relationship between the cooling nozzle and the limiting roller of the present invention. In the present invention, the application to thick steel plates is mainly considered, and preventing the out-of-plane deformation generated during the cooling of the thick steel plates becomes an important issue. Therefore, from the viewpoint of preventing out-of-plane deformation, a method is set to cool the thick steel plate S while limiting it with the limiting roller 4 and the roller 3. At this time, it is advantageous to prevent the out-of-plane deformation of the steel plate when the spacing (limiting roller spacing P) of the limiting roller 4 relative to the conveying direction is as narrow as possible. In addition, from the viewpoint of appropriately preventing out-of-plane deformation, the limiting roller diameter D of the limiting roller 4 is preferably as large as possible in order to reduce the deflection of the limiting roller 4 even if a large load is applied. On the other hand, the narrower the limiting roller spacing P of the limiting roller 4 is configured, the narrower the roller spacing G is, and therefore the smaller the space for setting the cooling device 2. Therefore, in the case of a nozzle that requires a large cooling manifold as described in Patent Document 3, the setting of a cooling device as in the present invention becomes impossible. Furthermore, from the viewpoint of uniform cooling, in order to cool the steel plate S to the vicinity of the contact point between the limiting roll 4 and the thick steel plate S, it is preferred that the spray length L when the cooling nozzle 53 (or the cooling nozzle 54) is viewed from the side is expanded compared to the roller interval G so that the thick steel plate S is exposed to cooling water to the area below the limiting roll 4. From such a viewpoint, a method such as jet cooling that can spray cooling water over a wide area is also preferred.

[0061] Based on the above viewpoints, the inventors have carefully studied and found that, from the perspective of shape control of the steel plate, the ratio P / D of the limiting roller spacing P and the limiting roller diameter D of the limiting roller 4 is set to a range below 2.5. It should be noted that when P / D is 1.0, the limiting roller spacing is the same as the limiting roller diameter, there is no gap between the front and rear limiting rollers, and a cooling nozzle cannot be set. Therefore, P / D is preferably greater than 1.0, and the gap (PD) between the front and rear limiting rollers can be ensured to be at least 50 mm. Therefore, from an operational point of view, P / D is more preferably set to 1.17 or more. Moreover, from the point of view of shape control, P / D is as small as possible, so it is preferred to set P / D to less than 2.0.

[0062] It should be noted that the roller diameter of the roller table roller 3 and the limiting roller diameter D do not have to be the same diameter. Whether the roller diameter of the roller table roller 3 and the limiting roller diameter D are the same or different on the upper and lower surfaces of the thick steel plate, as long as the ratio P / D is less than 2.5 as described above. In addition, as for the roller pitch and roller diameter of the roller table roller 3 on the lower surface of the thick steel plate, as long as the ratio is less than 2.5.

[0063] In addition, when the spray length L of the cooling nozzle 53 (54) in the conveying direction between the limiting rollers 4 is as close as possible to the limiting roller pitch P, the non-cooling portion between the limiting rollers 4 is reduced, and effective cooling can be performed. Therefore, it is preferable that the spray length L is at least greater than the roller pitch G. On the other hand, in order to increase the spray length L, it is necessary to increase Figure 4 The spray angle θ of the cooling nozzle 53 (54) is shown. At this time, if the spray angle θ of the cooling nozzle 53 (54) is excessively increased, or the cooling nozzle 53 (54) is set in a state where the nozzle center axis of the cooling nozzle 53 (54) deviates from the central position between the limiting rollers 4 in the conveying direction (the left and right direction in the drawing), the spray water 55 (56) from the cooling nozzle 53 (54) collides with the limiting rollers 4 before colliding with the thick steel plate S, and there is a possibility that the thick steel plate S cannot be effectively cooled. Therefore, it is preferable to select an appropriate spray angle θ, and with respect to the nozzle center axis of the cooling nozzle 53 (54), it is preferable to arrange the nozzle center axis of the cooling nozzle 53 (54) within ±10 mm from the central position between the limiting rollers 4 relative to the conveying direction (the left and right direction in the drawing), and it is most preferable to arrange it at a substantially central position between the limiting rollers 4.

[0064] Next, the cooling header of the cooling device 2 will be described. Figure 5 (a) is a schematic diagram of the cooling device 2 of the present invention observed from above, and is a diagram for explaining the structure of the cooling header. A plurality of large-flow cooling nozzles 53 are installed along the width direction of the steel plate on the large-flow cooling header 51. On the other hand, a plurality of small-flow cooling nozzles 54 are installed along the width direction of the steel plate on the small-flow cooling header 52.

[0065] In the present invention, cooling nozzles having different flow rates per unit area and per unit time are configured. It should be noted that the flow rates per unit area and per unit time referred to herein refer to the flow rates of cooling water sprayed within the range of the interval P' between adjacent cooling nozzles. Hereinafter, the flow rates per unit area and per unit time are referred to as flow density (unit: L / (min·m 2 )).

[0066] That is, Figure 5 As shown in (a), cooling nozzles with a large flow density are installed on the large flow cooling manifold 51, and cooling nozzles with a small flow density are installed on the small flow cooling manifold 52, so that the cooling nozzles adjacent to each other in the width direction are respectively connected to the cooling manifolds of different systems.

[0067] It should be noted that in the present invention, cooling nozzles with different flow densities are arranged adjacent to each other in the width direction. The large flow cooling nozzles 53 and the small flow cooling nozzles 54 only need to be arranged in a row in the width direction of the thick steel plate S at a predetermined pitch.

[0068] In the present invention, when the cooling speed of the steel plate is accelerated, in order to avoid spraying cooling water from the small flow cooling nozzle 54, the water supply to the small flow cooling header 52 is cut off by the flow regulating valve 7, and cooling water is sprayed from the large flow cooling nozzle 53. On the other hand, when the cooling speed is slowed down, in order to avoid spraying cooling water from the large flow cooling nozzle 53 by the flow regulating valve 7, the water supply to the large flow cooling header 51 is cut off by the flow regulating valve 7, and cooling water is sprayed from the small flow cooling nozzle 54. That is, in the present invention, by individually selecting each cooling water supply system to spray cooling water, the flow rate can be adjusted in a wide range, and the cooling speed can be adjusted in a wide range.

[0069] Generally, when a nozzle having certain characteristics is selected and cooling water is sprayed from the nozzle, the flow rate of the cooling water is proportional to the 0.5 power of the spray pressure, so even if the spray pressure is reduced, the change in the flow rate is small, and it is very difficult to change the cooling rate significantly. Generally, it can be said that the cooling rate is proportional to about 0.7 power of the flow density. Therefore, the cooling rate is proportional to about 0.35 power of the spray pressure.

[0070] Thus, for example, in order to reduce the cooling rate to about half, the injection pressure needs to be reduced to about 1 / 7. In a general flow control valve, the injection pressure can be adjusted to a range of about 10 to 100% of the rated value, so the cooling capacity can be adjusted to about 50 to 100% at most, which is the actual limit. Moreover, the injection flow rate is proportional to the 0.5 power of the injection pressure, so when considering that the injection pressure can be adjusted within a range of about 10 to 100% as described above, the adjustment of the injection flow rate within a range of 31.6 to 100% is the limit. Therefore, in the present invention, by configuring cooling nozzles with different flow densities between the limiting rollers 4, a wide range of cooling rate adjustment can be performed.

[0071] In the present invention, the flow densities of cooling water sprayed from adjacent cooling nozzles along the width direction of the steel plate are set to different flow densities, and for the same spray pressure, the cooling nozzle spraying cooling water with the largest flow density can spray cooling water with a flow density three times or more than that from the cooling nozzle spraying cooling water with the smallest flow density. Figure 5 In (a), the flow density of the large flow rate cooling nozzles 53 arranged at a pitch P' is at least three times higher than that of the small flow rate cooling nozzles 54 at the same injection pressure.

[0072] Next, a specific method of selecting cooling nozzles will be described by taking the case of spraying cooling water from dual-system cooling headers as an example.

[0073] When the nozzle spacing of the large flow cooling nozzle 53 and the small flow cooling nozzle 54 in the steel plate width direction is set to the same and cooling water is sprayed at a pressure of 0.4 MPa, the flow density of the large flow cooling nozzle 53 is selected to be 1500 L / (min·m 2 ), the flow density of the small flow cooling nozzle 54 is selected to be 500L / (min·m 2 With such a structure, the flow rate can be controlled by using the flow rate regulating valve 7, thereby adjusting the flow rate density of the large flow rate cooling nozzle 53 to 500L / (min·m 2 ) (1 / 3 of the rated value), adjust the flow density of the small flow cooling nozzle 54 to 167L / (min·m 2 Therefore, by controlling the flow rate and switching the cooling nozzle, the maximum flow density of the large flow cooling nozzle can be increased from 1500L / (min·m 2 ) to the minimum flow density of the small flow cooling nozzle 167L / (min·m 2) is continuously adjusted until the flow rate is adjusted. It should be noted that in the manufacture of steel plates, when the flow density of the large flow cooling spray and the small flow cooling nozzle 54 does not need to be adjusted continuously as described above, the maximum flow density of the small flow cooling nozzle 54 does not need to be the same as the minimum flow density of the large flow cooling nozzle 53. For example, the maximum flow density of the large flow cooling nozzle 53 may be 1500L / (min·m 2 ), so that the maximum flow density of the small flow cooling nozzle 54 is 50L / (min·m 2 ) such a choice.

[0074] In this way, by selecting one cooling header of a system by the flow rate regulating valve 7 and spraying cooling water from the cooling nozzles, it is possible to continuously adjust the spray water amount over a wide range.

[0075] In the present invention, cooling nozzles with different flow densities are arranged adjacent to each other, and only one of them is made to spray, so the arrangement is such that, for example, Figure 5 (b) Figure 5 (c) is a flat spray shape that sprays in a fan shape. Figure 5 In (b), the spray angle θ is set so that the width end of the spray water 55 sprayed from the large flow cooling nozzle 53 is substantially at the same position as the adjacent spray water 55 (see Figure 4 ) and the torsion angle α (refer to Figure 5 (c)), so that when the steel plate passes through the cooling, when viewed from the steel plate side, there is no portion in the width direction where the cooling water does not collide with the steel plate, and the steel plate can be cooled uniformly.

[0076] in addition, Figure 5 The same is true for the case (c). By setting the spray angle θ (see FIG. 1 ) so that the width end of the spray water 56 sprayed from the small flow cooling nozzle 54 is substantially at the same position as the adjacent spray water 56, Figure 4 ) and the torsion angle α (refer to Figure 5 (c)), so that when the steel plate passes through the cooling, when viewed from the steel plate side, there is no portion in the width direction where the cooling water does not collide with the steel plate, and the steel plate can be cooled uniformly.

[0077] As the spray angle θ of the cooling nozzle (large flow cooling nozzle 53 or small flow cooling nozzle 54), it is preferred to set the cooling nozzle between the narrow limiting rollers 4 to avoid the sprayed cooling water colliding with the limiting rollers 4 and causing the steel plate to be exposed to water, so it is preferred to be able to spread at as wide an angle as possible. In the present invention, the spray angle θ of the cooling nozzle (refer to Figure 4) is at least 60 to 120 degrees. When the spray angle θ is less than 60 degrees, the cooling water cannot be spread over a large area, so there may be temperature unevenness caused by the non-collision part of the cooling water. On the other hand, this is because when the spray angle is greater than 120 degrees, the flight distance of the spray water to the steel plate varies greatly between the flight distance just below the nozzle and the flight distance to other parts, making it difficult to ensure uniform cooling.

[0078] In addition, use Figure 3 , indicating the distance from the front end of the cooling nozzle to the steel plate (nozzle height H). Regarding the distance between the cooling nozzle (large flow cooling nozzle 53 or small flow cooling nozzle 54) and the thick steel plate S, when considered from the point of collision between the limiting roller 4 and the spray water, the closer the front end of the cooling nozzle is to the steel plate, the more difficult it is for the cooling water to collide with the limiting roller 4 even if it is sprayed at a large spray angle θ. In particular, when the distance between the cooling nozzle and the thick steel plate S is greater than half of the limiting roller diameter D where the gap between the limiting rollers 4 is the narrowest, the spray water from the cooling nozzle is likely to collide with the limiting roller 4 in the smallest gap between the limiting rollers 4. Therefore, the distance between the cooling nozzle and the thick steel plate S is preferably as low as possible from a position near half of the limiting roller diameter D (radius). On the other hand, when the distance between the front end of the cooling nozzle and the thick steel plate S is close, the spray water must be sprayed at a large angle, and there is a risk that the spray angle θ shown above exceeds 120°. In addition, there is also a risk that the front end of the steel plate in the through plate collides with the front end of the cooling nozzle. Considering practicality from both points of view, when cooling thick steel plates, the distance H from the front end of each cooling nozzle to the steel plate is preferably the distance from the center axis of the limiting roller on the upstream and downstream sides of the steel plate conveying direction relative to the nozzle to the steel plate, and the front end of the nozzle is set at a position within ±50 mm relative to the height of the center axis of the limiting roller.

[0079] In the above, an example of adjusting the cooling speed by the flow density of the dual system of the large flow cooling nozzle 53 and the small flow cooling nozzle 54 is described, but the present invention can be applied as long as there are more than two systems. Figure 6 In this way, the cooling header system is multiplied (four systems) and the cooling rate can be adjusted in a wider range.

[0080] exist Figure 6 In addition to the large flow cooling header 51 having a plurality of large flow cooling nozzles 53 installed along the width direction of the steel plate and the small flow cooling header 52 having a plurality of small flow cooling nozzles 54 installed along the width direction of the steel plate, medium flow cooling headers 57 and 58 are also configured. A plurality of medium flow cooling nozzles 59 and 60 are installed in the medium flow cooling headers 57 and 58 respectively along the width direction of the steel plate.

[0081] As Figure 6The specific method for selecting the cooling nozzle in the case of setting the nozzle spacing in the width direction of each cooling nozzle to be the same and spraying at a pressure of 0.4 MPa, so that the flow density of the large flow cooling nozzle 53 is 1500 L / (min·m 2 ), the flow density of the medium flow cooling nozzle 59 is set to 150 L / (min·m 2 ), the flow density of the medium flow cooling nozzle 60 is 40L / (min·m 2 ), the flow density of the small flow cooling nozzle 54 is 10L / (min·m 2 ). Thus, a difference of at least three times in flow density is set for the cooling nozzle with the largest flow density and the cooling nozzle with the smallest flow density for the same injection pressure. With such a structure, the flow rate can be controlled by using the flow regulating valve 7, so that the cooling speed can be adjusted continuously over a wide range.

[0082] In the present invention, each cooling nozzle is preferably any one or more of a flat nozzle, a full cone nozzle, a square spray nozzle, and an elliptical spray nozzle.

[0083] It should be noted that the spray angle of each cooling nozzle refers to an angle at which the spray angle becomes the widest in each direction when the sprayed water is viewed from the side. Figure 7 This is a diagram showing a situation in which the spray water 55 ( 56 ) from the cooling nozzle 53 ( 54 ) collides with the thick steel plate as viewed from above. Figure 7 (a) is a flat nozzle that sprays in a roughly fan-shaped manner and has a thin (about 20 mm) and wide collision surface. Figure 7 (b) is an example of an elliptical nozzle whose collision surface is elliptical. In the case where the collision surface of the cooling water is elliptical, such as a flat nozzle or an elliptical nozzle, Figure 7 As shown in (a) and (b), the angle extending along the long axis direction of the collision surface becomes the widest angle, so this angle can be used as the injection angle. Figure 7 In a full cone nozzle with a circular collision surface such as (c), the spray angle is the same no matter from which direction the nozzle is viewed from the side. Figure 7 In the case of a square spray nozzle whose collision surface is a rectangle (square or oblong) as in (d), the angle of expansion in the diagonal direction of the collision surface is the widest angle, and therefore, this angle may be used as the spray angle.

[0084] In addition, if Figure 8 As shown, the nozzle installation pitches in the width direction of the large flow rate cooling nozzle 53 and the small flow rate cooling nozzle 54 may be different nozzle pitches. Figure 8(a) is a diagram showing the structure of the cooling header when the installation pitch of the small flow rate cooling nozzles 54 is set to twice the installation pitch in the width direction of the large flow rate cooling nozzles 53, Figure 8 (b) is a diagram showing the spraying of water by the large flow rate nozzle 53. Figure 8 (c) is a diagram showing the spray water of the small flow cooling nozzle 54. Figure 8 (b) and (c) are the cases where all nozzles are flat nozzles. For example, as an example where the flow density is more than 3 times, when the flow density of the large flow cooling nozzle 53 is 4 times the flow density of the small flow cooling nozzle 54, when spraying at a pressure of 0.4 MPa, the maximum flow density of the large flow cooling nozzle 53 becomes 1500 L / (min·m 2 ), the minimum flow density of the small flow cooling nozzle 54 becomes 375L / (min·m 2 ).

[0085] It should be noted that the large flow rate cooling nozzle 53 and the small flow rate cooling nozzle 54 may also be set to different spray forms.

[0086] The above description is based on the example of the off-line heat treatment process of thick steel plates. Fig. 9 In this way, the slab is heated by the heating furnace 1, rolled into a predetermined size by the rolling mill 8, and then cooled by the cooling device 2 having a cooling header 5 between the limiting rolls 4 as in the present invention. It should be noted that in order to smoothly convey the thick steel plate S just after rolling to the cooling device 2, it is preferred to convey the steel plate to the cooling device 2 after flattening it in advance by the hot straightening machine 9.

[0087] It should be noted that the cooling device of the present invention can be preferably used for a thick steel plate having a plate thickness of 4.0 mm or more and a plate width of 100 mm or more.

[0088] Therefore, if the manufacturing equipment of the thick steel plate is provided with the cooling device of the present invention, the shape of the thick steel plate can be controlled and the cooling rate can be adjusted in a wide range, so the thick steel plate with various strengths can be manufactured. Moreover, according to the cooling method of the present invention, the shape of the thick steel plate can be controlled and the thick steel plate can be cooled at a wide range of cooling rates, so if the manufacturing method is provided with a step of cooling the thick steel plate using the cooling method of the present invention, the thick steel plate with various strengths can be manufactured.

[0089] Example 1

[0090] As a first embodiment of the present invention, using Figure 1The off-line heat treatment equipment for thick steel plates shown in the figure produced thick steel plates. After heating a steel plate (thickness 25 mm, plate width 3500 mm, steel plate length 7 m) at room temperature to 920°C in a heating furnace 1, the plate passing speed was adjusted in a cooling device 2 located 2.5 m behind the heating furnace 1 so that the steel plate temperature became 100°C and the plate was cooled. The structure of the cooling device 2 is similar to that of the Figure 2 Similarly, the diameter of the roller 3 and the limiting roller 4 is set to 300 mm, the roller pitch P between the roller 3 and the limiting roller 4 is set to 600 mm, and cooling nozzles 53 and 54 (P / D=2.0) are provided between the limiting rollers 4. It should be noted that 15 cooling nozzles 53, 54 and limiting rollers 4 are provided in the conveying direction of the steel plate (the length of the cooling device 2 is 9.0 m).

[0091] In addition, the arrangement of the cooling nozzles 53 and 54 is similar to Figure 3 Similarly, the distance between the cooling nozzle and the steel plate is set to 200mm. The large flow cooling nozzle 53 is set to a flat nozzle that sprays at a spray pressure of 0.4Mpa and 150L / min. The spray angle θ of the large flow cooling nozzle 53 is set to 100°, the width direction spacing P´ of adjacent large flow cooling nozzles 53 is set to 160mm, and the torsion angle α is set to 48° in the direction of travel of the steel plate. At this time, the flow density of the large flow cooling nozzle 53 when the spray pressure is 0.4MPa becomes 1563L / (min·m 2 ). The small flow cooling nozzle 54 is set as a flat nozzle that sprays at a spray pressure of 0.4 MPa and 40 L / min. The spray angle θ of the small flow cooling nozzle 54 is set to 100°, the width direction spacing P´ of adjacent small flow cooling nozzles 54 is set to 160 mm, and the torsion angle α is set to 48° in the direction of steel plate travel. At this time, the flow density of the small flow cooling nozzle 54 when the spray pressure is 0.4 MPa becomes 417 L / (min·m 2 ).

[0092] Fig.10 : is a graph showing the relationship between the injection pressure and the flow rate density of the large flow rate cooling nozzle 53 and the small flow rate cooling nozzle 54 .

[0093] First, when water is passed through the large flow cooling header 51 and the injection pressure of the large flow cooling nozzle 53 is gradually reduced from 0.4 MPa, the pressure can be adjusted by the flow regulating valve 7 until the injection pressure reaches about 0.04 MPa. However, if the pressure is lower than this, the pressure fluctuates greatly due to the subtle difference in the opening of the flow regulating valve 7, so the pressure cannot be stably adjusted. The flow density of the large flow cooling nozzle 53 is 1563 L / (min·m 2 ), when the injection pressure is 0.04MPa, it is 494L / (min·m2 ).

[0094] Next, the water flow through the large flow cooling header 51 was stopped and the water flow through the small flow cooling header 52 was started. The flow density of the small flow cooling nozzle 54 when the injection pressure was 0.4 MPa was 417 L / (min·m 2 ), it can be seen that cooling water with a flow density approximately the same as the lower limit of the large flow cooling nozzle 53 can be sprayed. Furthermore, when the spray pressure of the small flow cooling nozzle 54 is gradually reduced from 0.4MPa, the pressure can be adjusted to about 0.04MPa by using the flow regulating valve 7. However, if the pressure is lower than this, the pressure fluctuates greatly due to the subtle difference in the opening of the flow regulating valve 7, and the pressure cannot be stably adjusted. The flow density of the small flow cooling nozzle 54 is 132L / (min·m 2 ).

[0095] from Fig.10 The results showed that a wide range of spray water volumes can be achieved by using cooling nozzles with different flow densities.

[0096] Next, Fig.11 The figure shows the relationship between the cooling rate and the flow density when the steel plate is actually cooled from 800°C to 400°C at the center in the plate thickness direction. Fig.10 The same structure as in the case of . Scanning radiation thermometers (not shown) are set on the input and output sides of the cooling device to measure the surface temperature of the steel plate in the plate width direction and the length direction. Based on the information from the thermometers on the input and output sides, the average temperature of the steel plate in the plate thickness direction is calculated by heat transfer calculation, and the cooling rate during the water cooling process is calculated. The cooling rate is the measurement result of the central part of the plate width and the central part of the length direction of the steel plate as the cooling rate of the center of the steel plate.

[0097] like Fig.11 As shown, by using a large-flow cooling nozzle 53 for cooling, the cooling rate can be adjusted in the range of about 20 to 30°C / s, and by using a small-flow cooling nozzle 54 for cooling, the cooling rate can be adjusted in the range of about 7 to 20°C / s. It can be seen that the cooling rate can be adjusted in a wider range compared to the case where each cooling nozzle is used as a single unit.

[0098] Example 2

[0099] As a second embodiment of the present invention, similar to the first embodiment, a steel plate (thickness 25mm, plate width 3500mm, steel plate length 7m) at room temperature was heated to 920°C by a heating furnace 1, and then cooled by adjusting the plate passing speed in a cooling device 2 located 2.5m behind the heating furnace 1 so that the steel plate temperature became 100°C, and the cooling rate from 800°C to 400°C at the center in the plate thickness direction and the temperature deviation in the width direction of the cooled steel plate were studied. It should be noted that the temperature deviation in the width direction was measured using a scanning radiation thermometer at 20mm intervals in the width direction and 100mm intervals in the length direction, and the value in the center of the length direction of the steel plate was taken as the temperature deviation in the width direction.

[0100] The structure of the cooling device 2 Figure 2 Similarly, the diameters of the roller table roller 3 and the limiting roller 4 are shown in Table 1. Moreover, both the large flow nozzle 53 and the small flow nozzle 54 use flat nozzles, and the spray angle θ, the width direction pitch P', and the twist angle α are shown in Table 1. Moreover, the length of the cooling device 2 is set to 9.0m, and the number of the limiting roller 4 and the cooling nozzle 53 (54) is shown in Table 1.

[0101] [Table 1]

[0102]

[0103] Regarding Examples 1 to 8, the cooling rate can be adjusted within a range of about 20 to 30°C / s by cooling with the large flow cooling nozzle 53, and the cooling rate can be adjusted within a range of about 7 to 20°C / s by cooling with the small flow cooling nozzle 54. It should be noted that the temperature deviation in the plate width direction at this time was less than 15°C. Then, the strength of the cooled raw material was measured, and it was at a level with no particular problem in terms of quality.

[0104] Regarding Examples 9 to 16, the cooling rate can be adjusted within a range of about 20 to 30°C / s by cooling with the large flow cooling nozzle 53, and the cooling rate can be adjusted within a range of about 7 to 20°C / s by cooling with the small flow cooling nozzle 54. It should be noted that the temperature deviation in the plate width direction at this time is less than 20°C. Although the temperature deviation is slightly larger than when P / D is 2.0, it is a level that does not cause any particular problem in quality when the strength of the cooled raw material is measured later.

[0105] Comparative Examples 1 to 8 are examples in which the spacing P between the limiting rollers is larger than that of Examples 1 to 8. P / D is 3.0, which is outside the scope of the present invention. The cooling rate can be adjusted in the range of about 20 to 30°C / s by cooling with a large flow cooling nozzle 53, and the cooling rate can be adjusted in the range of about 7 to 20°C / s by cooling with a small flow cooling nozzle 54. On the other hand, under all conditions, the steel plate is deformed into a wave shape. It can be considered that during the cooling operation, when the limiting roller 4 on the input side of the cooling device 2 is visually observed, there is a gap between the limiting roller 4 and the steel plate, and the cooling water leaks from the gap to a part of the width direction, locally cooling the steel plate. Moreover, the temperature deviation in the width direction of the plate after cooling varies in the range of 27 to 60°C. When the strength of the cooled raw material is measured later, the hardness of the steel plate at the location where the leaked water adheres increases, and there are problems in quality.

[0106] Comparative Examples 9 to 16 are examples in which the roller diameter D is reduced relative to Examples 1 to 8 of the present invention. P / D is 2.7, which is outside the scope of the present invention. The cooling rate can be adjusted in the range of about 20 to 30°C / s by cooling with a large flow cooling nozzle 53, and the cooling rate can be adjusted in the range of about 7 to 20°C / s by cooling with a small flow cooling nozzle 54. On the other hand, under all conditions, the steel plate deforms into a wave shape. It is considered that during the cooling operation, when the limiting roller on the entry side of the cooling device is visually observed, there is a gap between the limiting roller and the steel plate, and cooling water leaks from the gap to a part of the width direction, cooling the steel plate. Moreover, the temperature deviation in the width direction of the plate at this time varies in the range of 35 to 60°C. When the strength of the cooled raw material is measured later, the hardness of the steel plate at the location where the leaked water adheres increases, and there are problems in quality.

[0107] Description of symbols

[0108] 1 Heating furnace

[0109] 2 Cooling device

[0110] 3 Roller table rollers

[0111] 4 Limit rollers

[0112] 5 Cooling header

[0113] 51 High Flow Cooling Manifold

[0114] 52 Small flow cooling header

[0115] 53 High flow cooling nozzle

[0116] 54 Small flow cooling nozzle

[0117] 55 Spray water

[0118] 56 Spray water

[0119] 57 Medium Flow Cooling Header

[0120] 58 Medium Flow Cooling Header

[0121] 59 Medium Flow Cooling Nozzle

[0122] 60 Medium Flow Cooling Nozzle

[0123] 6 Flow meter

[0124] 7 Flow control valve

[0125] 8 Rolling mill

[0126] 9. Heat straightening machine

[0127] S Thick Steel Plate

[0128] P Limit roller spacing

[0129] D Limit roller diameter

[0130] G Roller Interval

[0131] L Spray length

[0132] H Nozzle height

[0133] P´ (widthwise) spacing

[0134] θ Injection angle

[0135] α Twist angle.

Claims

1. A cooling device for thick steel plates, which is a cooling device in which a plurality of limiting rollers are arranged along the conveying direction of the steel plates and a plurality of cooling headers are arranged between the limiting rollers, wherein: The ratio P / D of the limiting roller pitch P to the limiting roller diameter D is set to be 2.0 or more and 2.5 or less. Each cooling header is connected to any one of two or more cooling water supply systems. Each cooling water supply system is equipped with a regulating valve to independently open and close the water supply and control the flow rate. A plurality of cooling nozzles are installed along the width direction of the steel plate on each cooling header. Each cooling nozzle is any one or more of a flat nozzle, a full cone nozzle, a square nozzle, and an elliptical nozzle. When cooling water is sprayed from each cooling nozzle, the spray angle of the cooling water is in the range of 60 to 120 degrees. The adjacent cooling nozzles along the width direction of the steel plate are respectively connected to the cooling headers of different cooling water supply systems, and, The flow densities of cooling water sprayed from adjacent cooling nozzles along the width direction of the steel plate are set to different flow densities. For the same spraying pressure, among the adjacent cooling nozzles along the width direction of the steel plate, the cooling nozzle spraying cooling water with the largest flow density can spray cooling water with a flow density three times or more than that from the cooling nozzle spraying cooling water with the smallest flow density. The cooling device for a thick steel plate includes a control mechanism that performs control using a regulating valve so as to individually select each cooling water supply system and spray cooling water from a cooling nozzle.

2. The cooling device for thick steel plates according to claim 1, wherein: The distance from the tip of each cooling nozzle to the steel plate is set at a position within a range of ±50 mm or less with respect to the height of the center axis of the regulating roll.

3. A method for cooling a thick steel plate, using a cooling device having a plurality of limiting rollers arranged along the conveying direction of the steel plate and a plurality of cooling headers arranged between the limiting rollers, wherein: The ratio P / D of the limiting roller pitch P to the limiting roller diameter D is set to be 2.0 or more and 2.5 or less. Each cooling header is connected to any one of two or more cooling water supply systems. Each cooling water supply system is equipped with a regulating valve to independently open and close the water supply and control the flow rate. A plurality of cooling nozzles are installed along the width direction of the steel plate on each cooling header. Each cooling nozzle is any one or more of a flat nozzle, a full cone nozzle, a square nozzle, and an elliptical nozzle. When cooling water is sprayed from each cooling nozzle, the spray angle of the cooling water is in the range of 60 to 120 degrees. The adjacent cooling nozzles along the width direction of the steel plate are respectively connected to the cooling headers of different cooling water supply systems, and, The flow densities of cooling water sprayed from adjacent cooling nozzles along the width direction of the steel plate are set to different flow densities. For the same spraying pressure, among the adjacent cooling nozzles along the width direction of the steel plate, the cooling nozzle spraying cooling water with the largest flow density can spray cooling water with a flow density three times or more than that from the cooling nozzle spraying cooling water with the smallest flow density. Each cooling water supply system is individually selected and controlled by using a regulating valve so that cooling water is sprayed from the cooling nozzle.

4. The method for cooling a thick steel plate according to claim 3, wherein: The distance from the tip of each cooling nozzle to the steel plate is set at a position within a range of ±50 mm or less with respect to the height of the center axis of the regulating roll.

5. A thick steel plate manufacturing facility comprising the cooling device according to claim 1 or 2.

6. A method for manufacturing a thick steel plate, comprising a cooling step using the cooling method according to claim 3 or 4.

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